The use of electrically conductive transvenous leads, particularly cardiac pacing leads, is well known in the medical field. Many different methods and tools have been proposed in the prior art for allowing such leads to be introduced into the patient's subclavian vein via a relatively small incision. Often, medical device manufacturers may provide an introducer set to be used by doctors in implanting pacing leads.
In U.S. Pat. No. 4,147,165 issued to Tauschinski on Apr. 3, 1979 and entitled "Separable Needle for Inserting a Catheter Into the Blood Stream" there is disclosed a separable metallic needle having an inner plastic sealing tube for preventing leakage of the needle during insertion into the patient's blood vessel. After the needle is inserted, the inner sealing tube is removed. Thereafter, a lead is inserted through the needle into the blood vessel, and the separable needle is removed.
In the U.S. Pat. No. 4,166,469 issued to Littleford on Sep. 4, 1979 and entitled "Apparatus and Method for Inserting an Electrode" there are described several different techniques for the introduction of a transvenous pacing lead. One technique involves first puncturing the skin into an internal blood vessel such as the subclavian vein. One end of a guide wire is inserted into the vein by passing the guide wire through the lumen of the needle, after which the needle is then removed leaving the guide wire in place. Next, an introducer and introducer sleeve or sheath are slid along the guide wire to enter the vein, and the introducer and guide wire are removed, leaving the introducer sleeve in place. The introducer sleeve has sufficient diameter to allow a pacing lead to then be inserted therein and fed into the subclavian vein. The introducer cannot be slid back along the lead as the needle was retracted over the guide wire, since the pacemaker lead has a connector coupling disposed on its end that cannot pass through the introducer sleeve. Accordingly, the introducer sleeve is longitudinally scored or otherwise adapted to be longitudinally severed once the pacing lead has been positioned.
This first technique is also described in U.S. Pat. No. 4,243,050 issued to Littleford on Jan. 6, 1981 and entitled "Method for Inserting Pacemaker Electrodes and the Like"; in U.S. Pat. No. 4,306,562 issued to Osborne on Dec. 22, 1981 and entitled "Tear Apart Cannula"; in U.S. Pat. Nos. 4,346,606, 4,345,606 to Littleford on Aug. 24, 1982 and entitled "Split-Sleeve Introducers for Pacemaker Electrodes and the Like"; in U.S. Pat. No. 4,411,654 issued to Boarini et al. on Oct. 25, 1983 and entitled "Peelable Catheter With Securing Ring and Suture Sleeve"; in U.S. Pat. No. 4,581,025 issued to Timmermans on Apr. 8, 1986 and entitled "Sheath"; in U.S. Pat. No. 4,596,559 issued to Fleischhacker on Jun. 24, 1986 and entitled "Break-Away Handle for Catheter Introducer Set"; and in U.S. Pat. No. 4,687,469 issued to Osypka on Aug. 18, 1987 and entitled "Device for Slitting Introducers For Pacemaker Electrodes".
A second technique described in the Littleford '469 reference involves a necessarily larger diameter needle that is inserted into the subclavian vein. An introducer sleeve may then be inserted within the internal passage or lumen of the needle and into the vein, and the needle withdrawn over the introducer. In this second technique, the introducer sleeve is similarly adapted to be longitudinally severed once the pacing lead has been positioned.
In a third technique described in the Littleford '469 reference, the inner diameter of introducer sleeve is sized to closely receive the outer surface of the needle, so that the needle and sleeve may be inserted into the vein simultaneously, and the needle then withdrawn.
A common feature of any method for introducing a lead into a patient's blood vessel is that a hollow, tubular instrument is required to provide a temporary passage or conduit into the blood vessel, through which the lead may be slid to enter the blood vessel. Such a conduit also allows blood to escape from the blood vessel, and may allow air to enter the blood stream, possibly leading to embolic complications.
In addition to the potential adverse clinical effects of leakage of blood and air through an introducer sheath, the flow of blood out of an introducer sheath is likely to make the physician's task more difficult, and may encourage the physician to perform the introduction procedure more hastily. This, in turn, can increase the tension associated with the introduction procedure, and the risk that mistakes will be made.
In the prior art, it is commonly suggested that the physician can prevent (or at least restrict) the flow of blood out of a introducer sleeve while the pacing lead is being prepared for introduction into the vein by placing his or her thumb over the exposed end of the introducer sleeve. This suggestion is made, for example, in the above-noted Littleford '050, Littleford '606, Timmermans '025, and Fleischhacker '559 patents. A similar "solution" to the leakage problem that is sometimes practiced in the art is to squeeze or pinch the exposed end of the introducer sleeve between the thumb and forefinger.
Neither of these methods for reducing the undesired flow of fluids and air through the introducer sleeve is deemed by the inventors to be entirely acceptable. In both cases, at least one of the physician's hands is required, thereby making it difficult for the physician to attend to other or more important matters. Moreover, squeezing the exposed end of the introducer sheath can deform or even break the introducer at that point, making lead insertion difficult and increasing the danger of damage to the lead as it passes through the introducer.
In addition, neither placing the thumb over end of the introducer, nor squeezing the end of the introducer, will be sufficiently effective in preventing the flow of blood and air in the introducer once a guide wire has been threaded through the introducer. Also, the configuration of the end of some types of introducer sheaths is such that it is difficult or impossible to seal the end of the introducer shut with the thumb.
A tricuspid valve system for catheter (as opposed to lead) introducers is also deemed to be unacceptable for use in conjunction with lead introducers. The tricuspid valve arrangement for catheters could damage the sensitive lead tip of a pacing lead. The application of pressure required to open the tricuspid value can result in distortion or breakage of the lead tip. Moreover, some presently known tricuspid systems are lubricated with silicone-based oil. The electrical properties of pacing/sensing leads, and the chemical properties of steroid-eluting lead tips and the like, can be severely effected by coming in contact with the oil.
It is believed by the inventors, therefore, that there is presently a need for a method and apparatus for preventing the undesired flow of air and blood in an introducer sheath prior to the insertion of a cardiac pacing or sensing lead.